4 Answers
4

Moin is short for Moin moin and means just Guten or Schönen and can therefore be used all day. In Northern Germany (well, Schleswig-Holstein at least) you'll encounter Moin moin all day as well though.

Note that Moin may also mean Morgen in Southern German dialects, not to be confused with Moin in Northern Germany...

By the way, Guten is also used informally when starting too eat, short for Guten Appetit. Don't use Moin in this context though ;)

From several vacations in northern Germany I've heard that a person entering a store or arriving at some location greets everyone already there by saying "Moin". Other people then return the greeting by responding "Moin Moin".

Just wanted to add that I'm pretty sure there's a regional factor in this as well. I'm from the Bremen/Oldenburg area, and "Moin" is definitely the common form and "Moin Moin" is very rare.

When I hear a "Moin Moin" it's either from someone from further north (i.e. Hamburg and beyond) or from a (usually older) person who grew up speaking platt - or from someone trying to mimic either of the aforementioned for (comic) effect...